Food Allergy Testing: What Does the Process Involve?

We are all familiar with allergies. Whether it’s allergies that come with the change of seasons, allergies to cats or dogs, or allergies to foods that include common allergens like gluten or dairy, most people have experienced allergies in one form or another. Sometimes, it’s obvious what is causing our allergies; we come into contact with a dog or dust and start sneezing. But other times, it isn’t so easy to find what is causing your discomfort. That’s where food allergy testing comes in. And you can get all your allergy testing and treatment at Asthma Allergy Center, in greater Portland, OR.﻿

Food Allergy Testing: The Process

Some people are lucky enough to not be allergic to anything, while others suffer through their allergies. Why do people have different reactions to the same substance? Well, allergies start when your body incorrectly mistakes a harmless substance for a dangerous invader. To help fight this “invader,” your body produces antibodies, specifically an antibody called Immunoglobulin E (IgE).

The IgE causes all those terrible symptoms we associate with allergies. Environmental allergies usually produce annoying, but ultimately harmless, symptoms: the runny nose and eyes, sneezing, coughing, and itching. Food allergies, however, besides causing moderate gastric reactions, can cause much more dangerous symptoms like swelling of the mouth, face, or throat, hives, and even anaphylaxis. Food allergies are taken so seriously because they can be deadly.

When to Use Food Allergy Testing

Some food allergies are known to be severe. Most people allergic to things like peanuts and shellfish will go into anaphylactic shock if they eat something containing these ingredients. These kinds of allergies are often diagnosed early in life and require lifestyle changes and sometimes, medical interventions in the forms of epi-pens. However, other food allergies can cause less severe reactions. You may experience food allergies in the form of bloating, constipation and diarrhea, nausea, acid reflux, and vomiting.

That’s where food allergy testing comes in. Millions of Americans have food allergies that are not easily identifiable. Using food allergy testing allows individuals to have their reactions to many allergens tested at once. This allows the doctor and patient to rule out possible allergens and determine the offending food.

What About False Negatives?

It’s possible for your food allergy test to result in a false negative. That is, it’s possible for you to have a food allergy, but not react to the testing. Skin tests, in particular, are known to be affected by false positives. This is because allergy medications can prevent allergy tests from giving accurate results.

If you are suffering from an unknown allergy, it’s likely you use over the counter medications to help manage your frustrating symptoms. These medications stay in your system for longer than you think, and even if you don’t take any allergy medications for days before your allergy test, these medications can still prevent you from getting the right results.

Usually, your doctor will ask you to stop taking any allergy medications for several days before the test. If skipping your allergy medication isn’t an option, your doctor may opt for a type of food allergy test that isn’t as easily affected by over the counter allergy medication.

How Does Food Allergy Testing Work?

When it comes to testing for food allergens, there are three main categories: skin tests, blood tests, and food challenges.

Skin Tests

Skin tests are the most common way that food allergy testing is done. That’s because these kinds of tests tend to be least painful and the easiest way to test for allergies, in addition to allowing the doctor to test for multiple allergies at a time. Skin tests can also be used to test for airborne allergens. There are several types of skin tests that your doctor may use to help narrow down your possible food allergies.

Skin Prick Test

Prick tests have the benefit of giving you a relatively immediate reaction to possible food-related allergens. This kind of testing for allergens does use needles, but they barely pierce the skin which makes the whole process pretty painless. The skin prick test is most commonly done on the forearm, but it can also be performed on your back. If you are testing for many possible food allergens, the health care professional may opt to use your back so there is more space for the test.

The health care professional will first clean your forearm or back with rubbing alcohol to make sure it is sterile. Then, they will draw marks on your skin to clarify the regions where your skin will be pricked. Next to the marks, they will put drops of various allergen extracts. Next, they will use a small needle to lightly puncture your skin to introduce the allergen extract. And to make sure that your skin is reacting normally, the health care professional will also apply two other things: histamine and saline or glycerin. Histamine causes an allergic reaction when it’s introduced to the skin, while saline and glycerin do not generally cause any reaction.

As previously explained, one of the reasons the skin prick test is so popular is because it causes a fast reaction. It only takes about 15 minutes for your skin to react to the possible allergens. If you are allergic to any of the allergen extracts that were introduced to your skin, you will most likely see a red, raised, itchy bump where needle pricked you. If you do develop bumps as a reaction to the allergens, they should clear in a couple of hours. Or you can take an antihistamine, like Benadryl, to help them clear faster.

Skin Injection Test

Like the skin prick test, the skin injection test also uses a needle to deliver a small amount of allergen extract to your skin. But unlike the prick test, the injection test goes a little deeper, and you may feel a small pinch when the needle enters your skin.

The skin injection test is often used if your doctor thinks you have a specific allergy, but your skin prick test came up negative. Delivering the allergen extract deeper into the skin can force a reaction when just pricking the skin did not. Again, the doctor will wait 15 minutes for your body to react to the allergen extracts, then examine your skin for results.

Patch Test

The patch test takes a longer time than other skin tests available. For this test, you wear patches containing allergens for about two days to see how your skin reacts. Your doctor will probably advise you to avoid activities while showering or doing activities that cause sweating while wearing the patches as this can damage their adhesive properties. After approximately 48 hours, you will go back to the doctor to have them remove the patches and inspect the skin beneath them.

Blood Tests

There are several reasons that your doctor may opt to use blood tests over skin tests. If you have had a severe allergic reaction in the past, it can be safer to do a blood test than a skin test. Your doctor also might choose to do a blood test if you are on allergy medication that could interfere with the results, or if you have a skin condition that makes it hard to do skin testing.

Instead of introducing allergens to your body, blood tests look for the presence of IgE antibodies in your system. However, because the test doesn’t involve introducing possible allergens to your body, the tests can be less sensitive. Additionally, blood tests can be more expensive to run than skin tests, so some insurance plans may only provide coverage for skin testing.

The process of having food allergy testing in the form of a blood test is the same as any other blood test. The medical professional will clean your skin with alcohol, draw your blood with a needle, and bandage you up. In a few days, they will call you with your results.

Food Challenge Tests

Food challenge tests are often used if skin or blood tests were inconclusive. They can also help doctors determine the level of your reaction to known allergies. On the day of your test, your doctor will probably have you not eat anything beforehand.

During the food challenge test, the doctor will have you start eating small amounts of whatever food they think may be causing your allergic reactions. The doctor will have you continue eating in intervals, usually about every 15 to 30 minutes, to allow your body enough time for a reaction to develop. The presence, as well as the severity, of the reaction, gives the health care professionals valuable information about your condition.

If you do start having an allergic reaction, the doctor will quickly treat you with the appropriate medication, like antihistamines or epinephrine.

After the Allergy Test

Once you’ve had your food allergy testing and the results are in, what happens? You’ll meet with your doctor to go over the results within the context of your medical history. The doctor won’t only focus on the allergens that you reacted to in your tests, but how these allergens relate to your medical history.

Patients who rarely come into contact with a specific food may have a reaction similar to that of an allergy because their bodies are not used to food. However, if you have never had symptoms after eating that food, it’s likely that this is a false positive. Using your medical history, the doctor will be able to determine which allergens are false positives and which are real allergies.

Together, you and your doctor can come up with an effective treatment plan to make your life easier. This may include figuring out how to avoid certain foods that you’re allergic to or introducing allergy medications to help manage your more moderate symptoms. And of course, if you have a severe allergy that could lead to anaphylactic shock, your doctor will educate you about the warning signs and effects of this, as well as teach you how to use an epi-pen.

Conclusion

Just like having any other unknown ailment, having undiagnosed food allergies can be an extremely frustrating and emotionally draining experience. Going through the motions of feeling sick without any real explanations or answers can be overwhelming for anybody. That’s why doing the food allergy testing and finding some answers is so important. Once you have answers, you can start to make a plan to help you live a healthier life without the constant presence of allergic reactions.

When you have food allergy testing, it’s important to remember that the tests must be viewed within the context of your medical history. Allergy tests can result in false positives and false negatives, and your doctor can help you work through these false results and determine exactly which allergens your body is reacting to. Even though allergy testing isn’t the most fun experience, it ultimately helps you lead a much healthier, happier, and more fulfilling life. If you’ve been considering seeing a doctor for food allergy testing, take that step. You will thank yourself in the long run.

For more on asthma and allergies, visit our website or give Asthma Allergy Center, in greater Portland, OR. Here to help you with all your allergy needs, we will walk you through the process of allergy testing and treatment!